The early evolution of the mammalian forebrain can be best examined by comparing the progressive changes occurring in brain morphology among ancestral mammal-like reptiles (therapsids). Endocranial brain casts are currently uncommon due to the lack of adequately prepared fossil skulls, their unavailability, and the generally held belief that the walls of the endocranium are poorly ossified. The purpose of this project is to prepare skulls acquired at the Smithsonian Institution for new brain casts using more modern techniques. Initial preparations indicate that the endocranium is complete enough to provide valuable and informative brain casts. In addition, it is clear that both carnivorous and herbivorous therapsids will have to be compared for an evaluation of the impact of life style (solitary vs. gregarious groups) upon brain morphology.